It is well known in motor vehicles to provide a car seat design having a height adjustable head rest and wherein the head rest is coordinated with a safety belt arrangement. The safety belt typically includes a lap and shoulder belt, whereby the shoulder belt is guided obliquely downward from an upper deflection or linkage point associated with the motor vehicle interior wall, to the head rest and then diagonally across the front side of the seat back to terminally connect with a buckle assembly. In such an arrangement, the head rest can be moved to a desired height position by hand or by a provided electric motor.
It is also known from the prior art that most users of these types of motor vehicle seats do not correctly adjust the height of the head rest, and thus, in the event of collision are subjected to an increased risk of "whiplash-type" injuries to the head and neck. German Patent Document DE 28 10 577 (corresponding to U.S. Pat. No. 4,285,545) discloses an automobile passenger seat having an automatically positionable head rest. Height adjustment for the head rest is dependent upon the fore-aft position of the seat with respect to a fixed point of reference associated with the seat's mounting points. Complex hydraulic and/or mechanical actuating means are used for the automatic height positioning of the head rest and operate on the assumption that larger persons require a higher arrangement of the head rest. Accordingly, a particular head rest height is associated with each seat position. A principal disadvantage with this technique for setting the head rest height is the reliance on the erroneous assumption that a driver/passenger always correctly positions the seat. Also, no allowance is made for the fact that some people have unusually long or short torsos and/or legs which of course effects the relationship of head rest height to its fore-aft seat positioning.
German Patent Document DE 30 21 126 (corresponding to U.S. Pat. No. 4,645,233) teaches to provide a first electric motor to a seat back to control the height adjustment for a head rest and a second electric motor to an upper seat belt deflection mounting assembly to adjust the height of the shoulder belt with respect the seat back. An infrared sensor assembly is also provided and is used to assist the seated passenger to control the height adjustment for both electric motors.
The above described prior art devices for automatically adjusting head rest height in combination with seat belt restraint systems are expensive to manufacture and implement in automobiles and, therefore, have not become common in practice.
Accordingly, there is a need in the art for an inexpensive safety seat belt restraint mechanism for motor vehicle seats which automatically adjusts the height of the head rest to a proper position in response to an accident and which can be realized with particularly simple structurally means. There is also a need in the art for an inexpensive height adjustable head rest and safety restraint configuration for auto motor vehicle seats whereby after an initial set-up adjustment for the passenger/driver is made, no further height adjustments are required.